The invention relates generally to a machine tool.
More particularly, the invention relates to a machine tool such as a rotary grinder, a lathe or the like in which a workpiece to be treated undergoes rotation.
A machine tool of this type may have a pair of spindles which rotatably support the workpiece, and a clamping device which grips one end of the workpiece. At least one of the spindles is driven and the clamping device is coupled to this spindle for rotation therewith by means of one or more entraining elements. The clamping device includes at least two clamping jaws which are mounted for movement in a guide plate and can releasably engage the end of the workpiece, and the clamping jaws are symmetrically displaceable relative to one another via square threads.
The clamping device resembles an annular jaw chuck and a conventional device of this type is constructed using spirally extending square threads. In such a conventional clamping device, two symmetrical discs having respective square threads are rotatably mounted on either side of a guide plate and can be rotated by means of a tightening key. This clamping device can only be tightened and loosened manually. The tightening key, which is inserted in the chuck transversely, can cause damage if it is not removed.
A similar device is disclosed in the West German Publication No. 35 32 942. Here, the clamping device must be set in a very specific angular position by means of a screwdriver in order to tighten and loosen the same. This requires time-consuming control. Moreover, the clamping device has a relatively expensive and bulky structure.